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Bertha, a tunnel boring drill, carving out what will be a four-lane highway in Seattle hit a roadblock Friday — and officials still don’t know what it is.

Considering that the five-story tall machine is designed to tunnel through rock and soil without issue, it’s puzzling as to what could have stopped it.

Bertha was photographed on her first day of tunneling. After boring 1,000 feet, she hit an unknown block Friday. Officials are still trying to determine what it is and how to remove it. (Image source: WSDOT/Flickr)

The Seattle Times described Bertha’s cutting face as “the widest in the world at 57 feet, 4 inches. At the depth that Bertha was boring — about 60 feet below the surface — the Times reported the earth should be a more refined sediment. Above that depth is more likely where obstructions, including century-old manmade objects, could reside.

Seeing some reports that I’m stuck. I’m working fine, but have encountered an obstruction. I’ll keep you posted.

This video shows a time lapse of the launch of Bertha to create the 1.7-mile tunnel under the city:

Options to remove the unknown obstruction include drilling down from the surface or sending crews in through the more than 1,000 feet that have been bored thus far to break up the object. This latter option, Washington Department of Transportion spokeswoman KaDeena Yerkan told the Times could be complicated by loose soil and pressurization issues.

“STP (Seattle Tunnel Partners) has not made a decision on how they’re going to move forward yet,” Yerkan told the Times Monday. “They’re talking to their experts, we have been talking to ours.”

As of Tuesday, the DOT released a statement saying it is still deciding upon how to safely deal with the block.